The claim the whole lecture is built on, and the argument Neville uses to make it concrete. A real belief, true or false, is what a man lives by - and he need not have had the experience to hold one. The demonstration is always the same and always physical: none of us has jumped from a tall building, and none of us doubts for a moment that it would be fatal or crippling. Elsewhere he uses the Empire State Building, or a razor drawn across the throat. In every case the point is that **believing and knowing have become one** - you cannot distinguish between them when the belief is real - and that this happens without any experience whatever. From this he draws two things. First a request: believe the testimony with the same intensity you believe you would die if you stepped off this house, even though you have not experienced either. Second a warning with real force in it, because the argument cuts both ways - a real belief may be a lie, and it will be lived by just as faithfully. The last war, he says, is the result of the belief in lies; every war and every violence is the belief in lies. That is why it matters so much what we are exposed to, and why he will say that nothing in this world is more important than that the testimony be heard.